psychology unit 4 aos1 sac

What is sleep?

A psychological construct that is broadly categorised as a naturally occurring altered state of consciousness.

How long is an average sleep episode?

8 hrs

How many sleep cycles are in one episode?

5

How long is each sleep cycle?

90 mins

What dies EEG stand for?

Electroencephalograph

What does Electroencephalograph (EEG) measure?

Detects, amplifies and records the electrical activity of the brain in the form of brainwaves.

What does EMG stand for?

Electromyograph

What does Electromyograph (EMG) measure?

Detects, amplifies and records the electrical activity of muscles.

What does EOG stand for?

Electro-oculograph

What does Electro-oculograph (EOG) measure?

Detects, amplifies and records the electrical activity of the muscles that control eye movements.

NREM Stage 1

• Transitional stage between wakefulness and sleep

• Lightest stage of sleep

• Brainwaves: alpha and theta waves

• Lower frequency and higher amplitude than beta waves

• Hypnic jerks may occur

• Easily awakened

NREM Stage 2

• Stage experienced most during a sleep episode

• Brainwaves: predominantly theta waves

• Sleep spindles: brief bursts of high-frequency brain activity

• K-complexes: single sharp high-amplitude, low-frequency wave

• Body functions continue to slow

• Deeper sleep than Stage 1

NREM Stage 3

• Deepest stage of sleep

• More common in the first half of the night

• Brainwaves: delta waves (low frequency, high amplitude)

• Very little muscle activity

• Difficult to wake

• Night terrors may occur

• Important for physical restoration and repair

REM Sleep

• Rapid eye movements occur

• Most vivid and memorable dreams occur

• Skeletal muscles become temporarily paralysed (sleep paralysis/atonia)

• Heart rate and breathing increase

• Makes up about 20% of sleep in adolescents and adults

• Important for mental restoration

Circadian Rhythm

• Biological rhythm lasting approximately 24 hours

• Regulates the sleep-wake cycle

• Controlled by the suprachiasmatic nucleus (SCN)

• Influenced by environmental cues (zeitgebers), especially light

• Affects alertness, body temperature and hormone release

Ultradian Rhythm

• Biological rhythm lasting less than 24 hours

• During sleep, refers to the repeating REM-NREM sleep cycle

• One sleep cycle lasts approximately 90 minutes

• Repeats several times throughout a sleep episode

Suprachiasmatic Nucleus (SCN)

• Cluster of neurons in the hypothalamus

• Acts as the body's master biological clock

• Receives information about light from the eyes

• Regulates circadian rhythms

• Controls melatonin production by signalling the pineal gland

Melatonin

• Hormone released by the pineal gland

• Promotes feelings of sleepiness

• Production increases in darkness

• Production decreases in light

• Helps regulate the sleep-wake cycle

Light, SCN and Melatonin Relationship

• Light enters the eyes

• Information sent to the SCN

• SCN signals pineal gland

• Melatonin production decreases

• Alertness increases

In darkness:

• SCN stimulates melatonin release

• Sleepiness increases

Partial Sleep Deprivation

• Inadequate sleep in quantity or quality

• Can occur over one or more nights

• Negatively affects affective, behavioural and cognitive functioning

Affective Effects of Partial Sleep Deprivation

• Increased irritability

• Mood swings

• Increased anxiety

• Reduced emotional regulation

• Increased stress sensitivity

Behavioural Effects of Partial Sleep Deprivation

• Slower reaction time

• Reduced motivation

• Increased errors

• Reduced productivity

• Greater risk-taking behaviour

Cognitive Effects of Partial Sleep Deprivation

• Reduced attention

• Poor concentration

• Impaired memory

• Slower thinking

• Poor decision-making

One Night of Full Sleep Deprivation

• Complete absence of sleep for one night

• Produces affective and cognitive impairments

Affective Effects of One Night of Full Sleep Deprivation

• Increased irritability

• Increased negative mood

• Reduced emotional control

• Heightened stress response

Cognitive Effects of One Night of Full Sleep Deprivation

• Reduced attention

• Poor concentration

• Impaired memory

• Slower information processing

• Poor judgement and decision-making

Delayed Sleep Phase Syndrome (DSPS)

• Circadian rhythm sleep disorder

• Sleep onset and waking times are delayed

• Person falls asleep and wakes later than desired

• Common in adolescents

Advanced Sleep Phase Disorder (ASPD)

• Circadian rhythm sleep disorder

• Sleep onset and waking times occur earlier than desired

• Person falls asleep and wakes very early

• More common in older adults

Bright Light Therapy

• Treatment for circadian rhythm sleep disorders

• Exposure to bright artificial light at specific times

• Resets the circadian rhythm

• Alters melatonin production

• Helps align sleep-wake patterns with desired times

Sleep Hygiene

Behaviours and environmental conditions that promote quality sleep

Daylight as a Zeitgeber

• External cue that helps regulate circadian rhythms

• Exposure to morning daylight promotes alertness

• Helps synchronise the sleep-wake cycle

Blue Light and Sleep

• Blue light suppresses melatonin production

• Increases alertness

• Exposure before bedtime can delay sleep onset

• Common sources include phones, tablets and computers

Temperature and Sleep Hygiene

• Cooler temperatures promote sleep onset

• Excessively hot or cold environments disrupt sleep

• Maintaining a comfortable bedroom temperature improves sleep quality

Eating Patterns and Sleep Hygiene

• Heavy meals close to bedtime may disrupt sleep

• Regular eating patterns support healthy circadian rhythms

• Avoid eating large meals immediately before sleep

Drinking Patterns and Sleep Hygiene

• Caffeine can delay sleep onset and reduce sleep quality

• Excessive fluid intake before bed may disrupt sleep

• Limiting caffeine and late-night drinks supports healthy sleep

Light regulating sleep chain

Light → Retina → SCN → Pineal Gland → Melatonin Release Changes → Sleep-Wake Cycle Regulated